Back in the days when Black was exclusively a screenwriter - at one stage the highest-paid in Hollywood - he was known around town for his self-reflexive tics, wherein he'd pepper his scripts with comments aimed straight at the reader. Take this aside, from page 107 of the script for The Last Boy Scout:

"INT. TOPANGA CANYON HOME - DAYRemember Jimmy's friend, Henry, who we met briefly near the opening of the film? Of course you do, you're a highly paid reader or development person."

If you think about how monotonous the average script reader's day is, it's no huge surprise Black's adrenalin-jolt approach paid off. What's surprising is that it took him as long as it did to take it on-screen. More than a decade after Boy Scout's release, Black made his directorial debut-cum-comeback with Kiss Kiss Bang Bang, a razor-sharp comedy noir that looked askance at its own script and its own genre.

"Okay, that is a terrible scene," our narrator-protagonist Harry (Robert Downey Jr) complains, after Val Kilmer's Gay Perry delivers a spot of heavy-handed exposition. "It's like 'Gee, why was that in the movie? You think maybe it'll come back later?'" It's the same trick Martin McDonagh tried with less success in last year's Seven Psychopaths - negating the deficiencies in your screenplay by acknowledging them in dialogue. Black's secret, if he has one, is ensuring that you're having too much fun to care.

Because before we get too tied up in knots discussing the metatextual merits of Kiss Kiss Bang Bang, we should emphasise just how much flat-out fun it is, and just how efficient it is as a modern-day LA potboiler. Black never uses the tongue-in-cheek aspect as an excuse to get sloppy, instead unfolding his hardboiled tropes - a world-weary private eye, a struggling actress, two seemingly unconnected murder mysteries - with skill and panache.

Narration aside, Downey Jr's Harry isn't close to a conventional noir hero; he's a small-time crook who stumbles first into an acting career and secondly into a labyrinthine murder investigation, reluctantly aided by Kilmer's jaded PI Perry (who's much closer to the Sam Spade model) and former high school crush-turned-failed actress Harmony (Michelle Monaghan).

It's an interesting performance from Downey Jr, in light of the stratospheric career renaissance he's had since; more vulnerable and less glib than anything we've come to expect from him. His tetchy, quotable bro-banter with Kilmer (who's literally never been better before or since) is half the film's beating heart, while watching Monaghan's game, gutsy turn makes you realise that by all rights she should have been the Emma Stone of the noughties.

The other half of Kiss Kiss Bang Bang's beating heart, what makes it more than a slick, dead-eyed genre exercise, is the unexpectedly sweet morality at its centre. Take this moment: Harmony mistakenly thinks Harry groped her while she was unconscious.

He's horrified, not by the false accusation but by how easily she brushes it off as no biggie. "The f**k kind of guys are you hanging out with?" he asks her, sadly. Later, his reaction to killing a man is similarly startling in its rawness. When Black's rapid-fire, salty patter lets you come up for air, it's only for long enough to punch you in the gut.